You are right. Somehow, I didn’t pay attention to the “j”. It works!
I just didn’t think it would matter, because it goes completely against Dorico’s concept of allowing for different chord suffixes for the same quality, like ma7, MA7, maj7, ^. Those can all be used interchangeably. So why not here?
I am very happy with typing m9^. Fast and easy.
Many thanks, Jesele, and let’s leave it there.